A servo motor

Abstract

A servo motor includes a housing, a stator, a rotor, an output shaft, and a spline sleeve. The spline sleeve is fixed to the rotor, and the output shaft is connected to the spline sleeve through an axial sliding spline pair, enabling the output shaft to have both rotational output torque and axial movement functions. An encoder is integrated inside the motor to monitor the rotational speed. Compared with the traditional injection molding machine drive system, this motor eliminates complex multi-stage transmission and directly drives the screw pre-plasticization, greatly improving transmission efficiency and reducing energy loss. The combined motion function of the output shaft meets the requirements of both rotational plasticization and axial movement of the screw during the injection molding process to adjust back pressure and feed quantity. The encoder monitors the rotational speed in real time, enabling precise control of the motor movement and improving injection precision. Meanwhile, the compact structure reduces the occupied space of the equipment, lowers maintenance costs and failure risks, effectively solves the problems of traditional solutions, and provides a more efficient and reliable drive solution for the injection molding industry.

Description

Technical Field

[0001] This invention relates to the field of servo motors, and in particular to a servo motor suitable for industrial equipment requiring complex motion control, such as injection molding machines and extruders. Background Technology

[0002] In injection molding machine production, the screw pre-plasticizing stage is crucial to the uniformity of plasticization and production efficiency. The traditional indirect drive method of "servo motor + reducer + transmission mechanism" has significant drawbacks: multi-stage transmission leads to high energy loss and low system efficiency; mechanical backlash and elastic deformation of the transmission chain cause dynamic response lag, affecting injection accuracy; and additional components such as reducers increase structural complexity and maintenance costs.

[0003] Screw pre-plasticizing requires combined motion control of rotational plasticizing and axial movement. However, ordinary servo motors can only perform single rotational motion, and axial movement relies on hydraulic or mechanical propulsion devices, which further increases the complexity and control difficulty of the system. Some improved solutions that integrate rotation and axial movement also have shortcomings, such as insufficient torque transmission capability of ball screw motors and low precision and poor heat dissipation of split dual-motion motors.

[0004] Taking the invention patent application No. 202410853413.8 (Publication No. 118456799A) as an example, although it achieves the reciprocating motion of the screw by driving the roller device through "servo motor + planetary reducer" and improves the torque output, the locking and steering control of the moving rod depends on mechanical tension feedback. The response delay of the servo motor will cause the screw steering adjustment to lag, affecting the plasticizing effect. Moreover, the gear meshing clearance of the planetary reducer will reduce the transmission accuracy during long-term operation.

[0005] In summary, the core problems of existing technologies lie in the backlash and elastic deformation introduced by multi-stage mechanical transmission, and the inability of single motion output to meet the demands of complex motion. Therefore, there is an urgent need for a servo motor that can directly drive and integrate complex motion control to solve the problems of low efficiency, slow response, and complex structure in traditional systems. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide a servo motor whose output shaft has both rotational output torque and axial movement functions, and can directly drive the screw of the injection molding machine for pre-plasticizing, thereby solving the problems of low transmission efficiency, slow response and complex structure of traditional solutions.

[0007] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: the servo motor includes a housing, a stator and a rotor built into the housing, and also includes an output shaft and a spline sleeve. The spline sleeve is fixedly connected to the rotor or integrally formed. The output shaft is connected to the spline sleeve through an axial sliding spline pair, so that a transmission structure with synchronous rotation and axial relative sliding is formed between the output shaft and the spline sleeve.

[0008] In order to form a complete and stable motor housing structure, provide a reasonable mounting base for internal components, and achieve good heat dissipation, the housing preferably includes a front flange, a liquid-cooled stator housing, and a rear flange. The front flange and the rear flange are respectively installed at the front and rear ends of the liquid-cooled stator housing, and together with the liquid-cooled stator housing, they form a complete housing structure. A front bearing is installed on the front flange, and a rear bearing is installed on the rear flange.

[0009] To ensure a secure installation of the spline sleeve and to guarantee the accuracy and smoothness of the transmission between the output shaft and the spline sleeve, preferably, the outer ring of the front bearing abuts against the front flange, and the inner ring of the front bearing is adapted to and connected to the spline sleeve.

[0010] In order to achieve accurate monitoring and feedback control of motor speed, preferably, the rear end of the rotor is also provided with a synchronously rotating tail shaft, and the inner ring of the rear bearing is connected to the tail shaft;

[0011] The motor also integrates an encoder for monitoring the motor speed. The encoder is a rotary encoder and is mounted on the tail shaft.

[0012] To lock the rotational movement of the output shaft when needed without affecting its axial movement, thus enhancing the safety and functionality of the motor in specific operating scenarios, a brake is preferably included. This brake is fitted around the outer circumference of the tail shaft to lock the rotational movement of the output shaft without restricting its axial movement. When the motor stops working or the rotational position of the output shaft needs to be fixed, the brake can function to prevent accidental rotation of the output shaft, avoiding potential safety hazards caused by its rotation. Conversely, when axial movement of the output shaft is required, the brake does not restrict it, thus meeting the diverse needs of the motor for output shaft movement under different operating conditions.

[0013] To reduce the number of parts, simplify the motor assembly process, improve the overall structural strength and stability, and reduce assembly errors, preferably, the spline sleeve, rotor, and tail shaft are connected as a single unit to form an integral rotor assembly, which is coaxially mounted in the inner rings of the front and rear bearings. This integral rotor assembly improves the overall strength and stability of the rotor and reduces potential points of failure.

[0014] To effectively reduce the stator temperature during motor operation, improve the motor's heat dissipation performance, and ensure the motor's stability and reliability during long-term operation, preferably, the liquid-cooled stator housing is equipped with cooling channels for liquid cooling of the stator. The coolant in the cooling channels can remove the heat generated by the stator, preventing the stator from overheating and causing performance degradation, thus extending the motor's service life.

[0015] To facilitate connection between the motor and external axially moving actuators, expand the motor's application scenarios, optimize the encoder's mounting position, and improve the motor's structural compactness, preferably, the rotor is connected to the rear end of the spline sleeve. The inner ring of the front bearing is fitted and connected to the spline sleeve, and the outer circumference of the rotor is connected to the inner ring of the rear bearing. A first opening is formed at the rear end of the rotor, creating a hollow cavity structure at the rear end of the motor for connecting external axially moving actuators. The encoder is mounted on the spline sleeve. This hollow cavity structure at the rear end of the motor facilitates connection to external actuators, allowing direct docking with components of equipment such as injection molding machines, simplifying the overall equipment structure. Mounting the encoder on the spline sleeve allows for more direct monitoring of the rotational state of the spline sleeve and output shaft, improving the accuracy of speed monitoring. It also optimizes the internal spatial layout of the motor, making the motor structure more compact and rational.

[0016] To achieve flexible axial movement and retraction of the output shaft, optimize the encoder mounting position, and improve the overall protection and applicability of the motor, preferably, the rotor is connected to the front end of the spline sleeve, the inner ring of the front bearing is adapted to the rotor, a second opening is formed at the front end of the rotor, the spline sleeve is installed at the rear end of the rotor and connected to the inner ring of the rear bearing, and the connecting end of the output shaft can retract into the motor from front to back through the second opening, with the encoder mounted on the rotor. In this structure, the output shaft connecting end can retract into the motor, effectively protecting the connecting end during motor operation, reducing the risk of external environmental influences, and extending service life; the encoder, mounted on the rotor, can directly monitor the rotor speed, providing more accurate data for the control system and facilitating more precise motor control; the overall structural design also improves the motor's applicability under different operating conditions, meeting diverse usage needs.

[0017] In order to ensure that the output shaft of the servo motor can be effectively locked in different applications, preferably, the front end of the front flange is provided with a brake to lock the rotational movement of the output shaft but not restrict its axial movement.

[0018] Compared with the prior art, the advantages of this utility model are as follows: By setting the output shaft and spline sleeve to be connected by an axial sliding spline pair, the motor output shaft has both rotational output torque and axial movement functions, which can directly drive the injection molding machine screw for pre-plasticizing. This avoids the multi-stage transmission in the traditional indirect drive method of "servo motor + reducer + transmission mechanism", significantly improving transmission efficiency and reducing energy loss. Since the mechanical backlash and elastic deformation in the transmission chain are eliminated, the motor response speed is greatly improved, enabling more precise control of the injection molding process and improving injection molding accuracy. At the same time, the integrated rotor module design makes the motor structure more compact, eliminating the need for additional reducers and complex transmission mechanisms, reducing equipment space occupation, and lowering equipment maintenance costs and failure risks. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of Example 1;

[0020] Figure 2 This is a schematic diagram of the structure after the output shaft is moved in Example 1;

[0021] Figure 3 This is a schematic diagram of the structure of Example 2;

[0022] Figure 4 This is a schematic diagram of the structure after the output shaft moves in Example 2.

[0023] Figure 5 This is a schematic diagram of the structure of Example 3;

[0024] Figure 6 This is a schematic diagram of the structure in Example 3 where the output shaft moves into the motor. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] Figures 1 to 6 The diagram shows three embodiments of this utility model. The servo motors in embodiments 1 to 3 all include components such as housing 1, stator 2, rotor 3, output shaft 4, spline sleeve 5, and encoder 6. The three different embodiments are described in detail below with reference to the accompanying drawings.

[0027] Example 1

[0028] This embodiment 1 corresponds to Figure 1 and Figure 2 It is suitable for most conventional injection molding machine screw pre-plasticizing scenarios, and has certain requirements for motor stability, speed control, and axial movement function. The structure and connection relationship of its components are as follows:

[0029] The housing 1 includes a front flange 1a, a liquid-cooled stator housing 1b, and a rear flange 1c. The front flange 1a and the rear flange 1c are respectively installed at the front and rear ends of the liquid-cooled stator housing 1b, forming a complete housing structure. A front bearing 1d is installed on the front flange 1a, and a rear bearing 1e is installed on the rear flange 1c.

[0030] The stator 2 is installed inside the liquid-cooled stator housing 1b, and the rear end of the rotor 3 is equipped with a synchronously rotating tail shaft 3a. A spline sleeve 5 is fixedly connected to the rotor 3, and connects the spline sleeve 5, rotor 3, and tail shaft 3a together to form an integral rotor assembly, which is coaxially mounted in the inner rings of the front bearing 1d and the rear bearing 1e. The outer ring of the front bearing 1d abuts against the front flange 1a, and its inner ring is fitted and connected to the spline sleeve 5; the inner ring of the rear bearing 1e is connected to the tail shaft 3a. It should also be noted that the spline sleeve 5 and rotor 3 can be connected separately, or, if the manufacturing process allows, can be integrally molded.

[0031] The output shaft 4 is connected to the spline sleeve 5 via an axial sliding spline pair, forming a transmission structure that allows synchronous rotation and axial relative sliding. The axial sliding spline pair includes involute spline teeth located on the outer circumference of the output shaft 4 and spline grooves machined into the inner hole of the spline sleeve 3. The encoder 6 is a rotary encoder, mounted on the tail shaft 3a, used to monitor the motor speed. The brake 7 is sleeved on the outer circumference of the tail shaft 3a to lock the rotational movement of the output shaft 4 but not restrict its axial movement.

[0032] It is equipped with a liquid cooling heat dissipation structure. By arranging cooling channels 1b1 inside the liquid-cooled stator housing 1b, the stator 2 can be cooled by liquid cooling.

[0033] The assembly process for each component is as follows:

[0034] First, install the front bearing 1d onto the front flange 1a, ensuring that the outer ring of the front bearing 1d is in tight contact with the front flange 1a. Next, install the front end of the assembly formed by the spline sleeve 5, rotor 3, and tail shaft 3a onto the inner ring of the front bearing 1d. Then, install the stator 2 inside the liquid-cooled stator housing 1b, connect the relevant circuits, and finally connect and secure the front flange 1a, which has the front bearing 1d and rotor assembly installed, to the liquid-cooled stator housing 1b.

[0035] Subsequently, the rear bearing 1e is installed on the rear flange 1c, and the rear flange 1c is connected and fixed to the rear end of the liquid-cooled stator housing 1b, while the inner ring of the rear bearing 1e mates with the tail shaft 3a. Then, the encoder 6 and the brake 7 are installed on the tail shaft 3a.

[0036] Finally, the output shaft 4 is connected to the spline sleeve 5 via an axial sliding spline pair. After this assembly, the front flange 1a is used to install the liquid-cooled stator housing 1b, and together with the spline sleeve 5 and the tail shaft 3a, it is installed on the inner rings of the front and rear bearings. When the motor is running, the output shaft 4 can transmit torque and also move freely axially. When the motor is not running, under the action of the brake 11, the output shaft 4 does not rotate but can rotate axially.

[0037] The working principle of the servo motor in Example 1 is as follows:

[0038] After the motor is powered on, current flows into the stator 2, generating a rotating magnetic field that interacts with the rotor 3, driving the rotor 3 to rotate. Since the spline sleeve 5 is fixedly connected to the rotor 3, the spline sleeve 5 rotates synchronously, thereby driving the output shaft 4 to rotate. The output shaft 4 transmits torque to the screw of the injection molding machine, realizing the pre-plasticizing rotation of the screw. During motor operation, the encoder 6 monitors the motor speed in real time and feeds the speed signal back to the control system. The control system adjusts the motor's input current according to the preset speed requirements to ensure the motor maintains a stable speed output, meeting the screw speed requirements of the injection molding process. When axial adjustment of the screw position is required, the control system controls the brake 7 to lock, allowing the output shaft 4 to move axially back and forth under external force through the axial sliding spline pair with the spline sleeve 5, thus achieving axial displacement adjustment of the screw. Specific application scenarios are as follows: During injection, the control system controls the brake 7 to lock, preventing the screw from rotating and only allowing axial injection movement; during pre-plasticizing, the control system controls the brake 7 to release, allowing the screw to rotate and move axially backward.

[0039] Meanwhile, the coolant circulates in the cooling channel 1b1 of the liquid-cooled stator housing 1b, carrying away the heat generated by the stator 2, ensuring that the motor maintains a suitable temperature during operation, and improving the reliability and service life of the motor.

[0040] Example 2

[0041] Example 2 corresponds to Figure 3 and Figure 4 It is suitable for injection molding machine applications that require connecting external axially moving actuators to the rear end of the motor and have special requirements for the utilization of space at the rear end of the motor.

[0042] Example 2 features a unique structural design. In this implementation, the rotor 3 is connected to the rear end of the spline sleeve 5, the inner ring of the front bearing 1d is fitted and connected to the spline sleeve 5, and the outer periphery of the rotor 3 is connected to the inner ring of the rear bearing 1e. The rear end of the rotor 3 has a first opening 3c, which creates a hollow cavity structure at the rear end of the motor. This structure is specifically designed to connect externally axially moving actuators, facilitating the functional expansion of the equipment.

[0043] In terms of component installation layout, unlike the first embodiment, the encoder 6 is mounted on the spline sleeve 5 instead of the tail shaft 3a. From an overall structural perspective, the front flange 1a houses the front bearing 1d, which supports the front end of the spline sleeve 5. The inner ring of the front bearing 1d is fitted with the spline sleeve 5, and the encoder 6 is mounted on the spline sleeve 5. The rear end of the rotor 3 is mounted in the inner ring of the rear bearing 1e, which is mounted on the rear flange 1c. The rear flange 1c is connected to the rear end of the liquid-cooled stator housing 1b, and a suitable fixing method ensures a stable connection. The output shaft 4 is mounted inside the spline sleeve 5, enabling torque transmission and axial movement. Due to the hollow cavity structure at the rear of the motor, the rear space is relatively large, facilitating the connection of axially moving actuators and meeting specific operational requirements.

[0044] The servo motor in Example 2 also differs from that in Example 1 in its operation. In Example 2, the encoder 6 monitors the rotational speed of the spline sleeve 5 to reflect the motor speed and feeds the speed signal back to the control system. The control system adjusts the motor's operating state accordingly to ensure stable screw speed. Due to the hollow cavity structure at the rear of the motor, the first opening 3c of the rotor 3 can be connected to external axially moving actuators, such as displacement sensors. These actuators can monitor the axial position of the screw in real time and feed the position signal back to the control system. Based on the position signal and injection molding process requirements, the control system controls the output shaft 4 to move axially through the axial sliding spline pair with the spline sleeve 5, thereby achieving precise adjustment of the screw's axial position. Furthermore, the location of the brake 7 also differs from that in Example 1. Here, the brake 7 is located at the front end of the flange 1a. (See reference [link to relevant documentation] for details.) Figure 5 As shown, the brake 7 is used to lock the rotational movement of the output shaft 4 but does not restrict its axial movement.

[0045] Example 3

[0046] Example 3 Corresponding Figure 5 and Figure 6 It is suitable for injection molding machine scenarios where there are special requirements for the overall layout of the motor and the connection method of the output shaft, and where the output shaft connection end needs to be protected and the structural layout optimized.

[0047] Example 3 also features a unique structural design, differing from Example 1 in structure and operation. Structurally, the rotor 3 is connected to the front end of the spline sleeve 5, and the inner ring of the front bearing 1d is fitted and connected to the rotor 3. A second opening 3d is formed at the front end of the rotor 3. The spline sleeve 5 is installed at the rear end of the rotor 3 and connected to the inner ring of the rear bearing 1e. The front bearing 1d is housed within the front flange 1a of the motor, and its inner ring mates with the shoulder of the rotor 3. The rear end of the rotor 3 is connected to the spline sleeve 5, and the inner ring of the rear bearing 1e is connected to the spline sleeve 5. The rear bearing 1e is installed within the rear flange 1c of the motor, which is connected to the rear end of the liquid-cooled stator housing 1b. The front end of the liquid-cooled stator housing 1b is connected to the front flange 1a. The output shaft 4 is connected to the spline sleeve 5. The output shaft 4 not only transmits torque but also allows axial movement, and its connecting end can retract from the second opening 3d into the motor from front to back. The encoder 6 is mounted on the rotor 3.

[0048] In Example 3, the encoder 6 monitors the rotational speed of the rotor 3 and feeds the speed signal back to the control system. The control system adjusts the motor's operating parameters based on the speed signal to ensure the screw speed meets the injection molding process requirements. When the screw position needs adjustment, the output shaft 4 can move axially through the axial sliding spline pair with the spline sleeve 5. Since the connection end of the output shaft 4 can retract into the motor from the second opening 3d of the rotor 3, the connection end of the output shaft 4 can be effectively protected during motor operation, avoiding the influence of the external environment and improving the reliability of the connection. The brake 7 is also located at the front end of the flange 1a, see the specific reference. Figure 6 As shown, the brake 7 is also used to lock the rotational movement of the output shaft 4 but does not restrict its axial movement.

[0049] It should be noted that in the description of this embodiment, the terms "front," "rear," "left," "right," "inner," "outer," "upper," and "lower," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A servo motor, comprising a housing (1), a stator (2) and a rotor (3) housed within the housing (1), characterized in that: It also includes an output shaft (4) and a spline sleeve (5). The spline sleeve (5) is fixedly connected to the rotor (3) or integrally formed. The output shaft (4) is connected to the spline sleeve (5) through an axial sliding spline pair, so that a transmission structure is formed between the output shaft (4) and the spline sleeve (5) that allows synchronous rotation and axial relative sliding.

2. The servo motor according to claim 1, characterized in that: The housing (1) includes a front flange (1a), a liquid-cooled stator housing (1b), and a rear flange (1c). The front flange (1a) and the rear flange (1c) are respectively installed at the front and rear ends of the liquid-cooled stator housing (1b) and together with the liquid-cooled stator housing (1b) form a complete housing structure. A front bearing (1d) is installed on the front flange (1a), and a rear bearing (1e) is installed on the rear flange (1c).

3. The servo motor according to claim 2, characterized in that: The outer ring of the front bearing (1d) abuts against the front flange (1a), and the inner ring of the front bearing (1d) is adapted to be connected to the spline sleeve (5).

4. The servo motor according to claim 2, characterized in that: The rotor (3) is also provided with a synchronously rotating tail shaft (3a) at its rear end, and the inner ring of the rear bearing (1e) is connected to the tail shaft (3a). The motor also integrates an encoder (6) for monitoring the motor speed. The encoder (6) is a rotary encoder and is mounted on the tail shaft (3a).

5. The servo motor according to claim 4, characterized in that: It also includes a brake (7), which is sleeved on the outer periphery of the tail shaft (3a) to lock the rotational movement of the output shaft (4) but not to restrict its axial movement.

6. The servo motor according to claim 4, characterized in that: The spline sleeve (5), rotor (3) and tail shaft (3a) are connected as a whole to form an integral rotor assembly, and are coaxially installed in the inner rings of the front bearing (1d) and rear bearing (1e).

7. The servo motor according to claim 2, characterized in that: The liquid-cooled stator housing (1b) is provided with cooling channels (1b1) for liquid cooling of the stator (2).

8. The servo motor according to claim 4, characterized in that: The rotor (3) is connected to the rear end of the spline sleeve (5). The inner ring of the front bearing (1d) is adapted to the spline sleeve (5). The outer circumference of the rotor (3) is connected to the inner ring of the rear bearing (1e). The rear end of the rotor (3) forms a first opening (3c), so that the rear end of the motor forms a hollow cavity structure for connecting external axially moving actuators. The encoder (6) is disposed on the spline sleeve (5).

9. The servo motor according to claim 4, characterized in that: The rotor (3) is connected to the front end of the spline sleeve (5), the inner ring of the front bearing (1d) is adapted to the rotor (3), the front end of the rotor (3) has a second opening (3d), the spline sleeve (5) is installed at the rear end of the rotor (3) and connected to the inner ring of the rear bearing (1e), the connecting end of the output shaft (4) can be retracted into the motor from front to back from the second opening (3d), and the encoder (6) is provided on the rotor (3).

10. The servo motor according to any one of claims 8 or 9, characterized in that: The front flange (1a) is provided with a brake (7) at its front end to lock the rotational movement of the output shaft (4) but not to restrict its axial movement.

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